Paleolithic cave art in the Basque Country is an irreplaceable resource for understanding the cultural and symbolic practices of prehistoric societies. Despite its significance, the conservation and protection of this heritage have often been treated as secondary concerns, which is alarming given that mechanical, physicochemical, and biological processes can erase these images from the archaeological record. The ProMeteo project arises to address these threats, particularly in the context of climate change, which has already led to annual average temperature increases of up to 1.5 ºC in some Basque caves over the last 20 years.
The main objective of the research is to prove, through controlled experimentation, that weathering processes can cause the irreversible loss of rock art images on stone supports exposed to the elements. Specific objectives include:
- Producing experimental mock-ups of common supports such as sandstone, limestone, and schist.
- Replicating engravings using three Paleolithic techniques (fine incision, deep incision, and pecking) to evaluate differential resistance.
- Subjecting these samples to accelerated weathering in climate chambers to simulate long-term environmental scenarios.
- Developing predictive models to extrapolate results to real-world conditions and guide conservation priorities.
Methodology
The study is organized into five main phases that integrate fieldwork, laboratory experiments, and computational modeling:
- Selection and Characterization: Three specific lithologies were chosen: sandstones from Bizkaia, Urgonian limestones, and schists from Salamanca. Thin sections will be used to analyze their mineral composition and porosity.
- Mock-up Preparation: Rocks will be cut into 5×5 cm blocks and engraved with standardized motifs to ensure comparability between samples.
- Climate Chamber Experimentation: Samples will be exposed to variations in temperature (-5 °C to 50 °C), humidity (20% to 95%), salt spray, and UV radiation. Three scenarios are defined: arid-saline, temperate-humid, and cold-snowy.
- Analytical Techniques: Researchers will use confocal microscopy to detect micro-cracks, close-range photogrammetry to measure volume loss, and colorimetry to identify chromatic changes.
- Data Modeling: Predictive statistical models will be developed to quantify the speed of degradation and estimate the rate of rock art loss in both real-time and future scenarios.
Expected Results
The project aims to produce data that will allow researchers to:
- Identify which factors (thermal, hydric, or saline) contribute most to the global degradation of each type of stone support.
- Establish a potential loss rate, helping to determine if the current record of open-air rock art is merely a fraction of what originally existed.
- Create a risk-prediction tool that heritage managers can use to design specific mitigation and protection strategies.
Conclusions
The ProMeteo project is innovative because, unlike traditional studies that only monitor the current state of heritage, it seeks to predict the future of rock art through scientific simulation. The research tests the hypothesis that weathering has biased our view of Paleolithic art by eliminating a large portion of works exposed to the outdoors. Validating this hypothesis would fundamentally change our understanding of prehistoric cultural history and provide the technical basis required to implement preventive conservation measures in the face of the global climate crisis